The long term objectives of this proposal are to determine the anatomical relationships between the retina and various retinal targets and to elucidate the rules that determine the organization of the retinal optic fibers in the pathways that lead them to their targets. This information will be applied to regenerating optic nerve axons to determine how the regeneration process leads to recovery of visual function. Such information may assist in establishing the methods and conditions necessary to achieve central nervous system regeneration in species that do not have this ability. Experiments are designed to determine whether in fact regenerating optic nerve fibers by-pass incorrect termination zones to terminate only in correct loci. In the course of these experiments, it will be determined whether different sectors of the retina normally project to different non-tectal retinal targets and whether different morphological types of retinal ganglion cells project to different targets. Another aim is to characterize the morphology of retinal ganglion cells and to examine the retinal ganglion cells to determine which cell types in which part of the retina lead the regenerative process. The methods to be used are both light and electronmicroscopy of optic axons filled with cobaltous-lysine. The cobalt method is extremely sensitive and is capable of filling optic axons at all stages of regeneration. It is also effective for retrogradely filling retinal ganglion cell bodies and dendrites when applied to the optic nerve. Radioautography will serve to complement the cobaltous-lysine method. Determining the projection of specific parts of the retina will be accomplished by applying cobaltous-lysine to a small retinal cut or by ablating part of the retina and applying cobaltous-lysine to the surviving axons from the intact part of the retina.